Tau Cygna V was the inhabited H-class fifth planet in the Tau Cygna system. This system was located over five thousand light years from the Sol Sector, within the de Laure belt. According to Section 133, Paragraph 77 of the Treaty of Armens, the planet had been ceded from the Federation to the Sheliak Corporate.
The planet was saturated with hyperonic radiation that made Human living very difficult, and often considered impossible. It contained mountains and desert landscape but also have water able to be collected. Rock slides were not unheard of.
In 2274, the colony ship SS Artemis headed for Septimis Minor, suffered failure of its guidance system, and went far off course, finding Tau Cygna V as the only suitable planet within reach on which to land. One third of the crew and passengers died of the radiation before they learned to adapt to it. The survivors established a new colony with their technology, building a town with living facilities in a desert area, made possible by an aqueduct with a pumping station originating on a nearby mountain. Many more died bringing water to the colony. They also cultivated large swaths of fields. The colonists remained lost to the Federation and completely unknown to the Sheliak as the colony grew over the next ninety-two years. At the colony, survival was valued over history, and while the colonists still knew their ancestors came from the Federation, some knowledge, such as what phasers were, was lost.
By 2366, the population had reached 15,253, descending from over three generations of the original settlers. Their leader at that time was Gosheven, who inspired further progress of the colony's growth.
During that same year, the colonists had to be evacuated due to the Sheliak discovering them on the planet while planning for their own colony to be placed there. The USS Enterprise-D was notified of the trespassing and subsequently Captain Jean-Luc Picard sent Lieutenant Commander Data to the surface in order to convince them it was futile to stay, as the Sheliak would simply kill them. While difficult, he succeeded and the colonists spent the next three weeks preparing for a Federation transport ship. After the evacuation, the Sheliak established their colony on the planet. (TNG: "The Ensigns of Command")